Certain air-conditioning apparatuses known in the prior art include a floor-installed unit, which is configured so that when a refrigerant having greater specific gravity when gasified than air leaks within the unit, the unit can be configured to form an accumulation of gas refrigerant near the bottom surface of the unit, and a refrigerant gas sensor can be installed in a location where the gas refrigerant can accumulate. For example, Japanese Patent No. 3744330 discloses an air-conditioning apparatus in which a refrigerant gas sensor is installed in proximity to a drain pan of the unit and refrigerant leakage occurring within the unit is detected.